Republicans have officially nominated Mitt Romney for president at the party's national convention in Tampa, Florida.

The former Massachusetts governor will challenge Barack Obama in November's presidential election.

Romney soared past the 1,144 votes threshold needed to secure his party's nomination on August 28.

Republican delegates from U.S. states and territories also formally nominated congressman Paul Ryan for vice president.

In the evening, Romney's wife, Ann, spoke to cheering supporters: "Let me say this to every American who is thinking about who should be our next president: no one will work harder, no one will care more, and no one will move heaven and earth like Mitt Romney to make this country a better place to live."

Ryan is scheduled to address the convention on August 29, while Romney's speech is due on August 30.

Opening the festivities in Tampa, Republican leaders condemned Obama's economic record and reminded voters of the country's high unemployment rate and ballooning budget deficit.

Party Platform

They approved a party platform calling for cutting taxes in order to stimulate the economy, ending abortion, and rejecting Obama's health care plan.

Reince Priebus, chairman of the Republican National Committee, warned that reelecting Obama would mean "four more years of failure." He said Romney and Ryan “will get this country working again."

Republican delegate Debra Forrest of Arizona told Reuters television, "I am so excited to be here and my thoughts about Mitt Romney are he is a fabulous leader. He will turn the economy around. He is courageous and he really will be the next president of the United States."

Recent opinion polls show Romney and the Democrat president locked in a tight race.

The Democrats will hold their own convention in North Carolina next week.

The Republican convention was delayed by a day amid concerns that tropical storm Isaac might disrupt the proceedings in Tampa.

The storm has since strengthened into a category one hurricane and made landfall in southeast Louisiana, heading toward New Orleans seven years after the city was devastated by Hurricane Katrina.